- 周彤;李梢;
This paper presents an algorithm for identifying desirable multiple targets in an intracellular regula- tion network. The algorithm is based on constrained state feedback and Monte-Carlo simulations. The com- putational complexity of the algorithm increases linearly with increasing the number of species in a gene regulation system. An estimate is derived for the confidence level of the predicted minimum required pertur- bation strength when targets are prescribed a priori. The algorithm has been used to analyze the cell cycle of Xenopus frog eggs. The results agree well with available results for single target perturbations, and multi- target interference is usually not equal to the summation of the single-target interferences.
2007年06期 629-637页 [查看摘要][在线阅读][下载 548K] [下载次数：163 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] <正>Introduction of School of Information Science and Technology (SIST)The School of Information Science and Technology (SIST) of Tsinghua University was founded in 1994, and consists of three Departments (Electronic Engineering, Computer Science and Technology, Automation), one Institute (Microe-lectronics), as well as the Research Institute of Information Technology, Joint Laboratory on Information Science and Technology, Tsinghua University Software College, and the National Training Center in Integrated Circuits.
2007年06期 637+657+662+668+677+690+699+746页 [查看摘要][在线阅读][下载 329K] [下载次数：17 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 宋阳秋;蔡渠棠;聂飞平;张长水;
This paper describes a semi-supervised regularized method for additive logistic regression. The graph regularization term of the combined functions is added to the original cost functional used in AdaBoost. This term constrains the learned function to be smooth on a graph. Then the gradient solution is computed with the advantage that the regularization parameter can be adaptively selected. Finally, the func- tion step-size of each iteration can be computed using Newton-Raphson iteration. Experiments on bench- mark data sets show that the algorithm gives better results than existing methods.
2007年06期 638-646页 [查看摘要][在线阅读][下载 2067K] [下载次数：129 ] |[网刊下载次数：0 ] |[引用频次：4 ] |[阅读次数：0 ] - 耿睿;程朋;
Dynamic airspace management plans and assigns airspace resources to airspace users on de- mand to increase airspace capacity. Although many studies of air traffic flow management (ATFM) have sought to optimally allocate air traffic to get the best use of given airspace resources, few studies have fo- cused on how to build an efficient air traffic network or how to adjust the current network in real time. This paper presents an integer program model named the dynamic air route open-close problem (DROP). DROP has a cost-based objective function which takes into account constraints such as the shortest occupancy time of routes, which are not considered in ATFM models. The aim of DROP is to determine which routes will be opened to a certain user during a given time period. Simulation results show that DROP can facilitate utilization of air routes. DROP, a simplified version of an air traffic network constructing problem, is the first step towards realizing dynamic airspace management. The combination of ATFM and DROP can facilitate decisions toward more reasonable, efficient use of limited airspace resources.
2007年06期 647-651页 [查看摘要][在线阅读][下载 445K] [下载次数：194 ] |[网刊下载次数：0 ] |[引用频次：11 ] |[阅读次数：0 ] - 丁子哲;张贤达;朱孝龙;
The paper analyzes the problem of blind source separation (BSS) based on the nonlinear principal component analysis (NPCA) criterion. An adaptive strong tracking filter (STF) based algorithm was devel- oped, which is immune to system model mismatches. Simulations demonstrate that the algorithm converges quickly and has satisfactory steady-state accuracy. The Kalman filtering algorithm and the recursive least- squares type algorithm are shown to be special cases of the STF algorithm. Since the forgetting factor is adaptively updated by adjustment of the Kalman gain, the STF scheme provides more powerful tracking ca- pability than the Kalman filtering algorithm and recursive least-squares algorithm.
2007年06期 652-657页 [查看摘要][在线阅读][下载 380K] [下载次数：105 ] |[网刊下载次数：0 ] |[引用频次：12 ] |[阅读次数：0 ] - 张玲;张贤达;
This paper describes a channel estimation and equalization algorithm using three-layer artificial neural networks (ANNs) with feedback for multiple input multiple output wireless communication systems. An ANN structure with feedback was designed to use different learning algorithms in the different ANN lay- ers. This actually forms a Turbo iteration process between the different algorithms which effectively im- proves the estimation performance of the channel equalizer. Simulation results show that this channel equalization algorithm has better computational efficiency and faster convergence than higher order statis- tics based algorithms.
2007年06期 658-662页 [查看摘要][在线阅读][下载 362K] [下载次数：72 ] |[网刊下载次数：0 ] |[引用频次：6 ] |[阅读次数：0 ] - 张玲;张贤达;
A multiuser detector was developed for fast fading code-division multiple-access systems by rep- resenting the channels as a system with the multiplicative noise (SMN) model and then using the known op- timal filtering algorithm for the SMN for multiuser detection (MUD). This multiuser detector allows the channel response to be stochastic in one symbol duration, which can be regarded as an effective method of MUD for fast fading CDMA systems. Performance analyses show that the multiuser detector is theoretically valid for CDMA systems over fast fading channels. Simulations show that the multiuser detector performs better than the Kalman filter-based multiuser detector with a faster convergence rate and lower bit error rate.
2007年06期 663-668页 [查看摘要][在线阅读][下载 415K] [下载次数：43 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 李细林;张贤达;李培胜;
The problem of approximate joint diagonalization of a set of matrices is instrumental in numerous statistical signal processing applications. This paper describes a relative gradient non-orthogonal approxi- mate joint diagonalization (AJD) algorithm based on a non-least squares AJD criterion and a special AJD us- ing a non-square diagonalizing matrix and an AJD method for ill-conditioned matrices. Simulation results demonstrate the better performance of the relative gradient AJD algorithm compared with the conventional least squares (LS) criteria based gradient-type AJD algorithms. The algorithm is attractive for practical appli- cations since it is simple and efficient.
2007年06期 669-673页 [查看摘要][在线阅读][下载 389K] [下载次数：55 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] - 李培胜;张贤达;苏泳涛;武露;
In orthogonal frequency-division multiplexing (OFDM) systems, the carrier frequency offset (CFO) destroys the orthogonality among subcarriers which degrades system performance. Various CFO estimation methods have been developed to compensate for the CFO at the receiver. This paper describes a novel minimum output variance method for OFDM systems with CFO in additive white Gaussian noise channels. This method utilizes the phase and the amplitude of the received signal and reduces the mean square error of the CFO by about 3 dB compared with the original minimum output variance method.
2007年06期 674-677页 [查看摘要][在线阅读][下载 347K] [下载次数：70 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 苏泳涛;张贤达;高秋彬;丁子哲;
Orthogonal frequency-division multiplexing (OFDM) systems are sensitive to carrier frequency off- set (CFO) which introduces intercarrier interference and significantly degrades system performance. This paper describes an iterative blind receiver consisting of a sequential Monte Carlo detector, a CFO estimator, and a compensator to reduce intercarrier interference. The framework is of low complexity due to the sepa- ration of tasks in a joint detection problem. In addition, the CFO estimator utilizes soft output of the sequen- tial Monte Carlo detector, which reduces the information loss caused by hard decisions and can obtain the CFO estimate in only one OFDM symbol. Simulation results demonstrate the effectiveness of the algorithm.
2007年06期 678-683页 [查看摘要][在线阅读][下载 395K] [下载次数：76 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] - 王生原;梁英毅;董渊;
Concurrent programs written in a machine level language are being used in many areas but verifi- cation of such programs brings new challenges to the programming language community. Most of the stud- ies in the literature on verifying the safety properties of concurrent programs are for high-level languages, specifications, or calculi. Therefore, more studies are needed on concurrency verification for machine level language programs. This paper describes a framework of a Petri net based safety policy for the verification of concurrent assembly programs, to exploit the capability of Petri nets in concurrency modeling. The con- currency safety properties can be considered separately using the net structure and by mixing Hoare logic and computational tree logic. Therefore, more useful higher-level safety properties can be specified and verified.
2007年06期 684-690页 [查看摘要][在线阅读][下载 349K] [下载次数：37 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 王海霞;汪东升;李鹏;王惊雷;李崇民;
Token protocol provides a new coherence framework for shared-memory multiprocessor systems. It avoids indirections of directory protocols for common cache-to-cache transfer misses, and achieves higher interconnect bandwidth and lower interconnect latency compared with snooping protocols. However, the broadcasting increases network traffic, limiting the scalability of token protocol. This paper describes an effi- cient technique to reduce the token protocol network traffic, called sharing relation cache. This cache pro- vides destination set information for cache-to-cache miss requests by caching directory information for re- cent shared data. This paper introduces how to implement the technique in a token protocol. Simulations us- ing SPLASH-2 benchmarks show that in a 16-core chip multiprocessor system, the cache reduced the net- work traffic by 15% on average.
2007年06期 691-699页 [查看摘要][在线阅读][下载 536K] [下载次数：67 ] |[网刊下载次数：0 ] |[引用频次：5 ] |[阅读次数：0 ] - 李鹏;汪东升;王海霞;路美娟;李崇民;郑纬民;
Memory limitations are always a focus of computer architecture. The live range aware cache (LIRAC) offers a way to reduce memory access using live range information. In the LIRAC system, scratch data need not be written back if the data will no longer be used. Three kinds of software support developed for LIRAC architecture use compiler analyses, binary analyses, and trace analyses. Trace analysis results show that LIRAC can eliminate 29% of cache write-backs on average and up to 83% in the best case for the SPEC CPU 2000 benchmark. These software techniques can show the feasibility and potential benefit of the LIRAC architecture.
2007年06期 700-706页 [查看摘要][在线阅读][下载 477K] [下载次数：34 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 秦伟俊;史元春;索岳;
Context-awareness enhances human-centric, intelligent behavior in a smart environment; however, context-awareness is not widely used due to the lack of effective infrastructure to support context-aware ap- plications. This paper presents an agent-based middleware for providing context-aware services for smart spaces to afford effective support for context acquisition, representation, interpretation, and utilization to ap- plications. The middleware uses a formal context model, which combines first order probabilistic logic (FOPL) and web ontology language (OWL) ontologies, to provide a common understanding of contextual in- formation to facilitate context modeling and reasoning about imperfect and ambiguous contextual informa- tion and to enable context knowledge sharing and reuse. A context inference mechanism based on an ex- tended Bayesian network approach is used to enable automated reactive and deductive reasoning. The middleware is used in a case study in a smart classroom, and performance evaluation result shows that the context reasoning algorithm is good for non-time-critical applications and that the complexity is highly sensi- tive to the size of the context dataset.
2007年06期 707-713页 [查看摘要][在线阅读][下载 854K] [下载次数：126 ] |[网刊下载次数：0 ] |[引用频次：9 ] |[阅读次数：0 ] - 张松海;张一飞;陈韬;Peter M. Hall;Ralph Martin;
Video structure analysis is a basic requirement for most content-based video editing and process- ing systems. This paper presents a fast video structure analysis method based on image segmentation in each frame, with region matching between frames. The structure analysis decomposes the video into sev- eral moving objects, including information about their colors, positions, shapes, movements, and lifetimes. The method also supports user interactions to improve the results. The result shows that this method is fast and stable and can complete video analyzing interactively.
2007年06期 714-718页 [查看摘要][在线阅读][下载 550K] [下载次数：52 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 张宇宙;王建勇;周立柱;
Parallel frequent pattern discovery algorithms exploit parallel and distributed computing resources to relieve the sequential bottlenecks of current frequent pattern mining (FPM) algorithms. Thus, parallel FPM algorithms achieve better scalability and performance, so they are attracting much attention in the data min- ing research community. This paper presents a comprehensive survey of the state-of-the-art parallel and distributed frequent pattern mining algorithms with more emphasis on pattern discovery from complex data (e.g., sequences and graphs) on various platforms. A review of typical parallel FPM algorithms uncovers the major challenges, methodologies, and research problems in the field of parallel frequent pattern discovery, such as work-load balancing, finding good data layouts, and data decomposition. This survey also indicates a dramatic shift of the research interest in the field from the simple parallel frequent itemset mining on tradi- tional parallel and distributed platforms to parallel pattern mining of more complex data on emerging archi- tectures, such as multi-core systems and the increasingly mature grid infrastructure.
2007年06期 719-728页 [查看摘要][在线阅读][下载 557K] [下载次数：57 ] |[网刊下载次数：0 ] |[引用频次：7 ] |[阅读次数：0 ] - 刘璘;金芝;
One of the difficulties that goal-oriented requirements analyses encounters is that the efficiency of the goal refinement is based on the analysts’ subjective knowledge and experience. To improve the effi- ciency of the requirements elicitation process, engineers need approaches with more systemized analysis techniques. This paper integrates the goal-oriented requirements language i* with concepts from a struc- tured problem analysis notation, problem frames (PF). The PF approach analyzes software design as a con- textualized problem which has to respond to constraints imposed by the environment. The proposed ap- proach is illustrated using the meeting scheduler exemplar. Results show that integration of the goal and the problem analysis enables simultaneous consideration of the designer’s subjective intentions and the physi- cal environmental constraints.
2007年06期 729-740页 [查看摘要][在线阅读][下载 916K] [下载次数：76 ] |[网刊下载次数：0 ] |[引用频次：6 ] |[阅读次数：0 ] - 潘立阳;孙磊;伍冬;陈军;许军;朱钧;
A 4 Mb embedded silicon-oxide-nitride-oxide-silicon (SONOS) memory was developed with a 0.18 μm CMOS logic compatible technology. A reverse programming array architecture was proposed to reduce the chip area, enhance the operating window, and increase the read speed. The charge distribution was analyzed to optimize the programming and erase conditions considering both the operating speed and the endurance performance. The final test chip has a good endurance of 105 cycles and a data retention time of at least 10 years.
2007年06期 741-746页 [查看摘要][在线阅读][下载 1036K] [下载次数：61 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 刘佳磊;梁仁荣;王敬;徐阳;许军;刘志弘;
The paper describes the growth of a germanium (Ge) film on a thin relaxed Ge-rich SiGe buffer. The thin Ge-rich SiGe buffer layer was achieved through a combination of ultrahigh vacuum chemical vapor deposition (UHVCVD) SiGe epitaxial growth and SiGe oxidation. A lower Ge content strained SiGe layer was first grown on the Si (001) substrate and then the Ge mole fraction was increased by oxidation. After removal of the surface oxide, a higher Ge content SiGe layer was grown and oxidized again. The Ge mole fraction was increased to 0.8 in the 50 nm thick SiGe layer. Finally a 150 nm thick pure Ge film was grown on the SiGe buffer layer using the UHVCVD system. This technique produces a much thinner buffer than the conventional compositionally graded relaxed SiGe method with the same order of magnitude threading dis- location density.
2007年06期 747-751页 [查看摘要][在线阅读][下载 1214K] [下载次数：47 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 叶佐昌;喻文健;余志平;
Transmission lines (T-Lines) are widely used in millimeter wave applications on silicon-based complementary metal-oxide semiconductor (CMOS) technology. Accurate modeling of T-lines to capture the related electrical effects has, therefore, become increasingly important. This paper describes a method to model the capacitance and conductance of T-Lines on CMOS multilayer, lossy substrates based on confor- mal mapping, and region subdivision. Tests show that the line parameters (per unit length) obtained by the method are frequency dependent and very accurate. The method is also suitable for parallel multiconductor interconnect modeling for high frequency circuits.
2007年06期 752-756页 [查看摘要][在线阅读][下载 428K] [下载次数：56 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - 杨彦甫;娄采云;
An ultrashort 10-GHz pulse generation scheme was successfully demonstrated using a bulk mate- rial InGaAsP electroabsorption modulator to generate the seed pulse. A self-phase modulation-based re- shaper was used after the adiabatic soliton compression in a comb-like dispersion profiled fiber. Experi- ments and simulations confirm that the reshaper effectively removes the pulse pedestal and improves the pulse extinction ratio. As a result, the 10-GHz pulse had no pedestal, a high extinction ratio, and a pulse width of only 1.4 ps.
2007年06期 757-760页 [查看摘要][在线阅读][下载 491K] [下载次数：41 ] |[网刊下载次数：0 ] |[引用频次：2 ] |[阅读次数：0 ] <正>~~
2007年06期 761-765页 [查看摘要][在线阅读][下载 228K] [下载次数：25 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ]